This invention relates to a data processing apparatus and a method used therein for correcting data errors.
In a variety of data processing apparatus, such as personal computers or word processors, a disk-shaped recording medium, such as a floppy disk, is widely used as the external storage medium.
The writing and reading of data in the floppy disk apparatus or unit is usually performed by the host computer issuing a series of control instructions to the floppy disk unit for sequentially actuating a variety of functional blocks such as rotary drive means or data processing means and the computer operation is performed sequentially in such a manner that, after the end of a predetermined control operation is ascertained, the computer proceeds to the next control operation.
In the conventional floppy disk apparatus or unit, it is therefore up to the host computer to control the operation of the disk apparatus or units from the start until the end of data recording and reproduction. Thus, a major portion of the processing capacity of the host computer is dedicated to controlling the disk unit operation so that the processing efficiency of the host computer is lowered considerably.
Furthermore, when correcting errors in the data recorded with error correction codes, flags are employed in the error correction or parity codes in the conventional triple erasure correcting routine in such a manner that, although the state of error correction is generally satisfactorily for random errors, the risk is high that a double error correction routine is executed upon the occurrence of burst errors, such that, when a 3-symbol error, for example, is taken for a 2-symbol error, the possibility is high that the correction is not feasible and the errors remain uncorrected.